A Mutually Assured Destruction
by Queerasil
Summary: Sherlock and Jim dance around each other for ages. When they finally collide, the results are catastrophically beautiful. Excerpt: Jim sits opposite from Sherlock. He stares at the empty chessboard, and Sherlock can see the gears inside his head whirling. Finally, he shrugs. "I give up. What's the deal." Sherlock leans forward. "Human chess," he says simply. (DarkLock Johnlock)
1. Chapter 1

_I gave you my number; thought you might call!_

Sherlock holds Jim's card in his hand, running the number over and over again in his mind. _Perhaps it's a code, or a trick, or a scheme of some kind?_

Sherlock punches the numbers in slowly, one by one. He pauses just before he hits the last one, wondering what John would say if he was here. He decides he doesn't care and presses it.

The phone rings out, and a mocking voice answers. "I've been expecting you."

Sherlock can't help smirking. "No, you weren't."

"No…" Jim's voice whispers, making the hairs on the back of Sherlock's neck stand up in the most unusual of ways. "I haven't. Honestly thought you already had a pet of your own."

"John, you mean?" Sherlock shrugs. "He's just practice. I'm just warming up for the real game."

"Foolish me! I thought we were already playing…"

Sherlock scoffs, "Please." Sherlock pauses. "We haven't even started yet."

Jim sounds positively delighted, "Everything before the pool was flirting. Now, we're just teasing. Foreplay, really."

"Intellectual foreplay. A teasing battle of the minds, if you will."

"Oh, I will. I gladly will, Sherly. I can call you that, can't I?"

Sherlock's voice is low and husky and deep enough to strike oil. "Only if you let me call you _Jim_."


	2. Chapter 2

Sherlock isn't sure why he agrees to meet Jim at the club.

He supposes it's 37% curiosity, 15% death wish, 11% compromise, 17% anger and 20% human error. The urge to solve the puzzle, the thrill of the game, the constant threat of death hanging over his head – he finds it all invigorating.

In the sea of writhing bodies, bad club music and disco lights, he finds Jim. His 'Jim from IT' persona hides him perfectly among the clubbers, and Sherlock barely notices when a new body begins to grind against his own.

"Didn't think you'd actually _come_." Jim whispers, drawing out the last word for added effect.

Sherlock groans. "I never break my promises."

"Good." Jim takes Sherlock by the hand, leading him through the crowd and to the bar. _Genius, _Sherlock thinks. _We'll just be two strangers flirting there. No one will suspect we're a consulting criminal and detective. _

Jim orders some fruity drink Sherlock's never heard of. "I have a little proposition to discuss with you," he says, casually. "I think we can be… Mutually beneficial to each other."

Sherlock leans on the bar. "Do tell."

"I'll solve cases for you. Or rather, give you information to solve cases, -"

"Your cases, I assume."

Jim smiles, his eyes full of menace. "Clever boy. Yes, 'my' cases - or rather – my client's cases. I'll give you everything you need to solve them, and go give me you."

Sherlock raises an eyebrow, not fully understanding what Jim means.

"Oh, Sherly, don't play coy. You know exactly what I mean." Moriarty winks.

Sherlock bites his lip. The offer is tempting, of course, but there are other, more important matters to consider. Mycroft, John, and all the Yarders will have to be sorted out. He'll need explanations, excuses, precautions – all to ensure total secrecy and safety. He can't go rushing into it. "I'll think about it," he responds, standing up and walking away without waiting for Jim's word.

Jim spins around on his barstool. "Don't take too long. Or else…" he laughs. "You get the point."


	3. Chapter 3

Sherlock walks back to the flat in silence. The night air is brisk and sharp and cold; a refreshing break from the hot, damp air of the club. The cold isolates him, helping his mind focus. Right now, he needs a distraction from Jim Moriarty.

Thank god for John Watson.

"Hey," John says, as soon as Sherlock walks in the door. He's still waiting up for him, even though it's 1:34 in the morning. "You were out late."

"And you're up late." Sherlock drops his coat carelessly on the floor and falls down onto the couch.

"Just… Typing," John sighs. _Poor John_, Sherlock thinks_. He's so in love with me it almost hurts_. "What were you out doing?"

"Case," Sherlock lies.

"Solved it?"

He smirks, closing his eyes. "Almost."

Sherlock starts seeing Jim everywhere. At crime scenes, restaurants, markets, shops, garages, and on the street. Jim is always disguised, of course. A true predator can always hide in plain sight.

One night, when John is sick, Jim joins Sherlock for dinner at Angelo's. Angelo brings them a candle for the table, and the whole thing would've been very romantic, providing that they weren't enemies.

They say nothing. They speak in stares, blinks, glimpses, and body language. Sherlock's mind races with information, reveling in the complex challenge Jim's very existence provides. Jim is a human puzzle, always changing, never staying the same.

"_I'm so changeable!" _Jim once said. How correct. What Jim doesn't know is, Sherlock is just the same.


	4. Chapter 4

_Baker Street. Come and play. SH_

When Jim arrives, John is out, and Sherlock has an empty chessboard and a pot of tea waiting on the table.

Jim sits opposite from Sherlock. He stares at the empty chessboard, and Sherlock can see the gears inside his head whirling. Finally, he shrugs. "I give up. What's the deal."

Sherlock leans forward. "Human chess," he says simply.

Jim smirks. "_Good_… Very good. The players?"

Sherlock looks positively delighted he has someone to play with. "We're both our respective Kings, able to make moves, but not willing to sacrifice ourselves to win the game. Mycroft is my Queen, Irene Adler yours. John is my Knight, Sebastian Moran yours. Lestrade is my Bishop, any of your crime bosses yours. Sally and Anderson are my rooks, two of your most trusted minions yours. The homeless network are my pawns, your network yours. Need I explain more?"

Jim is wide-eyed silent for a minute before he breaks out into hysterical laughter. "Brilliant," he wipes a non-existent tear from his eye. "Absolutely genius! Ah, I'm in love." He stretches his hands out to Sherlock, as if expecting an embrace.

Sherlock remains still. "Now, how shall we begin?"

Jim closes his eyes, licking his lips. "It all comes down to which of your little pieces I want to destroy first… I say… Pawn to E4."

…

In his Mind Palace, Sherlock has the scene set beautifully. They're standing across from each other in a great ballroom, and the floor is patterned black and white. Sherlock is black and Jim is white. Sherlock's pieces all stand perfectly still in their spots, waiting for commands, as do Jim's.

Jim's D4, an older looking man with grey hair, steps forward and takes his place.

"Pawn to D5," Sherlock says flatly. A young girl he knows to be named Emma steps forward. She's a new addition to his homeless network, recently orphaned, starving on the streets. He's determined not to lose her.

"Knight F3." Sebastian Moran stepped forward. A big, hulking man with arms ask thick as Sherlock's torso. There was no way Sherlock was letting John anywhere near him.

"Knight to C6." John stepped forward, his face devoid of emotion.

"Interesting," Jim mocked. "Such sentiment for your little pets." Jim shook his head. "_Tsk, tsk_, Sherly. This is all about sacrifice. "Bishop B5."

"Pawn to A6." Jim's Bishop is literally dropped kicked back to E3 by a member of Sherlock's homeless network, Grace. Sherlock smiles. Jim loses his turn, and Sherlock goes again. "Pawn to B5."

"Knight F6."

"Rook to E1." Sherlock's pawn is captured. The homeless man is dragged away kicking and screaming by the pawns.

Slowly, one by one, Sherlock and Jim's pawns pick each other off. John and Moran stay firmly planted in their spots. Sally decapitates Jim's rook, and Sherlock feels an enormous sense of affection for that woman.

Sherlock has six pieces left: Mycroft, Sally, Anderson, Lestrade, John, and (of course) himself. Jim has seven. The odds are statistically stacked against Sherlock, but that isn't stopping him.

_Sacrifice, _Sherlock ponders. Anderson can get Moran, but the resulting move will mean the Woman can get him.

Sherlock makes them move, apologizing as Anderson's neck is broken by a very determined Irene.

"Getting a bit sentimental, aren't you?" Jim taunts.

"Hardly." John can get to Jim, but only if he removes Moran. On the other hand, Sherlock could send Lestrade to kill Moran, putting the inspector in the line of fire. Risking John's life is the safer move, but he can't bring himself to do it. "Mycroft is to C3."

Mycroft steps forward and knocks Jim's bishop over with his umbrella. Sherlock feels familial sentiment and perhaps a little bit of pride for being his brother.

Moriarty looks slightly nervous now. "Rook to A7."

_Sorry, Sally, _Sherlock thinks. "Rook to A8."

Sally turns around and mouths _Freak_ just as she disappears from the board. Sherlock frowns. "Anderson to A8." Sherlock watches as Anderson punches the Rook, throwing her to the ground and beating her until she's black and blue. _Revenge. _

Moriarty smiles. "Seb A8." Seb walks over and promptly breaks Anderson's neck.

Sherlock winces. He looks over at his friend, "Lestrade to A8."

Lestrade kills Seb. Jim doesn't seemed surprised. "Some of us are willing to make sacrifices, Sherlock," he explains. "I thought you were one of them." Irene steps forward and obliterates Lestrade.

_Sorry. Sorry. Sorry. Sorry. _John can take out Irene, but then Jim would kill him.

_You have no other choice. You have to win the game._

_But you'll lose John._

_You'll lose everything else if you don't._

Sherlock has no choice. "John to F2."

John steps forward bravely.

Sherlock closes his eyes as Jim burns his heart out.

Mycroft kills Irene next.

Sherlock can't make the next move; he either has to sacrifice Mycroft or John.

Mycroft makes the decision for him and steps forward, kneeling before Moriarty.

Sherlock doesn't watch.

It's just Jim and Sherlock now. They dance around each other, but one step in each direction won't get you far. Soon, Jim is backed into a corner and Sherlock is standing before him proudly.

"You can't win," Jim smiles. "We'll be stuck like this forever. I'll always been one step ahead, and you'll always be one step behind. This. Will. Never. End."

Jim is right. Sherlock can't admit it. Won't admit it. The rules of the game are his to define and no one else's.

Sherlock steps forward to shake Jim's hand; Jim takes it reluctantly.

Suddenly, the chessboard dissolves and they're standing on the rooftop of Bart's, just teetering on the edge. Sherlock smiles and pulls Jim by the throat, whispering in his ear. "Don't talk to me about _sacrifice_," he spits.

Sherlock pulls them both over.

…

Sherlock opens his eyes. Jim is still sitting before him, a smile on his face. Quietly, the consulting criminal stands up and brushes nonexistent dust off his suit. "Well, this has been interesting." Jim holds out his hand to shake.

Sherlock smiles and takes his hand. "To our own mutually assured destruction."

…

**Notes:**

**Intensity level 4000000000000%.**

**The beginning of Jim and Sherly's game was modeled on the famous game between Oppenheimer and Einstein. **

**I hope you enjoyed!**


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